Karteikarten
Computer Paper 1: 1.2.1
Karten in diesem Stapel (24)
- 1What is an operating system?Programs or set of programs that manages operations of the computer. It acts as a bridge between the user & hardware.
- 2Functions of an operating system-Memory management
-Interrupt service routines
-Processor scheduling
-Management of input/output
-Backing store management - 3Memory managementPC allows user to work on several tasks at the same time.
Each program must be allocated a specific area of memory.
To switch from one program to another, they must be stored in memory. - 4What is the difference between a virtual (logical) and physical address?Physical addresses refer to hardware addresses of physical memory. Virtual addresses refer to the virtual store viewed by the process.
- 5Memory management: Paging Technique for optimum use of memoryMemory divided into fixed size pages of 4Kb.
Memory addresses stored on pages, a page table uses mapping to store a link between physical and logical address - 6Memory management: Segmentation Technique for optimum use of memorySplitting up of memory into logical sized divisions which vary in size. These are representative of the structure and logical flow of the program.
- 7Virtual MemoryWhen a section of hard drive used to act as RAM when space in main memory is insufficient to store programs being used.
Programs not in use temporarily moved into virtual memory by paging, freeing up memory for other programs in RAM. - 8Issue with virtual memoryDisk thrashing: when computer ‘freezes’ as a result of pages being swapped too frequently between hard disk and main memory.
More time spent transferring pages rather than running the program. - 9InterruptsSignals generated by software/hardware to indicate to processor that a process needs attention. When allocating processor time, urgency must be taken into consideration.
Interrupts stored in order of priority in a priority queue. - 10Interrupt Service Routine (ISR)CPU receives interrupt signal, suspends execution of all processes. Values in PC & each register onto system stack. ISR called to deal with interrupt.
Once interrupt serviced, values retrieved from stack and process resumes. - 11Processor schedulingComp can run programs at same time so OS must allocate processor time for each. While one runs, another can be queued.
Comp w/ 1 processor can only process 1 instruction at time but can give appearance of carrying out many tasks by carrying out small parts of large tasks in turns. - 12Scheduling: Round RobinEach process given time slice, if process not complete by end of time, then moves on to next process.
Interval timer used to generate interrupts at specific times.
Guarantees reasonable time to all users. - 13Scheduling: First come, First servedJobs processed in order that they arrive with no system priorities.
- 14Scheduling: Shortest remaining timeProcess w/ smallest estimated time to completion run next. This reduces number of waiting jobs.
Requires knowledge of how long job takes. - 15Scheduling: Multi-level feedback queuesImplements several job queues, jobs move between them depending on how much processor time they use. Ordered based on different priority.
Each queue has its own scheduling algorithm. - 16Scheduling: Shortest job firstProcess with smallest estimated running time run next.
- 17Types of OS: DistributedRun across multiple devices allowing load to be spread across multiple computer processors.
E.g. windows - 18Types of OS: EmbeddedBuilt to perform a small range of specific tasks, os catered to specific device.
Limited functionality.
E.g. Microwave, washing machine - 19Types of OS: Multi-taskingEnable user to carry out tasks seemingly at the same time. This is done using time slicing to switch quickly between programs.
- 20Types of OS: Multi-userMultiple users make use of one computer.
Scheduling algorithm must be used to prevent processor starvation. - 21Types of OS: Real timeUsed in time-critical systems, designed to perform task within a guaranteed time frame.
E.g traffic lights, self-driving cars - 22Basic Input Output System: (BIOS)First program that runs when computer turned on. Responsible for running key tests before OS can be loaded into memory.
E.g. Power-on self test (POST) ensures all hardware connected/ functional. - 23Device driverAllow OS to interact with hardware by sending request so OS can produce relevant output.
- 24Virtual MachinesInstance where software used to take on function of machine. E.g. executing intermediate code.
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- A level Computing (Computing Paper 1) Karteikarten am Computer Paper 1: 1.2.1, erstellt von Qashrina Collier am 03/05/2021.
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